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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Cardiovasc. Med.</journal-id>
<journal-title>Frontiers in Cardiovascular Medicine</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Cardiovasc. Med.</abbrev-journal-title>
<issn pub-type="epub">2297-055X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fcvm.2024.1490498</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Cardiovascular Medicine</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Elevated systemic immune-inflammatory index predicts poor coronary collateralization in type 2 diabetic patients with chronic total occlusion</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" equal-contrib="yes"><name><surname>Mao</surname><given-names>Lin Shuang</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/1332249/overview"/><role content-type="https://credit.niso.org/contributor-roles/formal-analysis/"/><role content-type="https://credit.niso.org/contributor-roles/software/"/><role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/></contrib>
<contrib contrib-type="author" equal-contrib="yes"><name><surname>Wang</surname><given-names>Yi Xuan</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/2199158/overview" /><role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/><role content-type="https://credit.niso.org/contributor-roles/formal-analysis/"/><role content-type="https://credit.niso.org/contributor-roles/software/"/></contrib>
<contrib contrib-type="author"><name><surname>Wu</surname><given-names>Zhi Ming</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/><role content-type="https://credit.niso.org/contributor-roles/data-curation/"/><role content-type="https://credit.niso.org/contributor-roles/investigation/"/><role content-type="https://credit.niso.org/contributor-roles/methodology/"/></contrib>
<contrib contrib-type="author"><name><surname>Ding</surname><given-names>Feng Hua</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/1959174/overview" /><role content-type="https://credit.niso.org/contributor-roles/data-curation/"/><role content-type="https://credit.niso.org/contributor-roles/investigation/"/><role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/><role content-type="https://credit.niso.org/contributor-roles/supervision/"/></contrib>
<contrib contrib-type="author"><name><surname>Lu</surname><given-names>Lin</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/1151135/overview" /><role content-type="https://credit.niso.org/contributor-roles/supervision/"/><role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/><role content-type="https://credit.niso.org/contributor-roles/methodology/"/><role content-type="https://credit.niso.org/contributor-roles/project-administration/"/></contrib>
<contrib contrib-type="author"><name><surname>Shen</surname><given-names>Wei Feng</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/1437779/overview" /><role content-type="https://credit.niso.org/contributor-roles/project-administration/"/><role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/><role content-type="https://credit.niso.org/contributor-roles/conceptualization/"/><role content-type="https://credit.niso.org/contributor-roles/validation/"/></contrib>
<contrib contrib-type="author"><name><surname>Dai</surname><given-names>Yang</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/1496106/overview" /><role content-type="https://credit.niso.org/contributor-roles/writing-original-draft/"/><role content-type="https://credit.niso.org/contributor-roles/funding-acquisition/"/><role content-type="https://credit.niso.org/contributor-roles/software/"/></contrib>
<contrib contrib-type="author" corresp="yes"><name><surname>Shen</surname><given-names>Ying</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="corresp" rid="cor1">&#x002A;</xref><uri xlink:href="https://loop.frontiersin.org/people/2833230/overview" /><role content-type="https://credit.niso.org/contributor-roles/funding-acquisition/"/><role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/></contrib>
</contrib-group>
<aff id="aff1"><label><sup>1</sup></label><institution>Department of Cardiovascular Medicine, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine</institution>, <addr-line>Shanghai</addr-line>, <country>China</country></aff>
<aff id="aff2"><label><sup>2</sup></label><institution>Institute of Cardiovascular Diseases, Shanghai Jiao Tong University School of Medicine</institution>, <addr-line>Shanghai</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by"><p><bold>Edited by:</bold> Vladimir M. Pisarev, V.A.Negovsky Research Institute of General Reanimatology, Russia</p></fn>
<fn fn-type="edited-by"><p><bold>Reviewed by:</bold> Jie Wu, Mayo Clinic Arizona, United States</p>
<p>Jayanta Gupta, Florida Gulf Coast University, United States</p></fn>
<corresp id="cor1"><label>&#x002A;</label><bold>Correspondence:</bold> Ying Shen <email>rjshenying8@163.com</email></corresp>
<fn fn-type="equal" id="an1"><label><sup>&#x2020;</sup></label><p>These authors have contributed equally to this work</p></fn>
</author-notes>
<pub-date pub-type="epub"><day>12</day><month>12</month><year>2024</year></pub-date>
<pub-date pub-type="collection"><year>2024</year></pub-date>
<volume>11</volume><elocation-id>1490498</elocation-id>
<history>
<date date-type="received"><day>03</day><month>09</month><year>2024</year></date>
<date date-type="accepted"><day>29</day><month>11</month><year>2024</year></date>
</history>
<permissions>
<copyright-statement>&#x00A9; 2024 Mao, Wang, Wu, Ding, Lu, Shen, Dai and Shen.</copyright-statement>
<copyright-year>2024</copyright-year><copyright-holder>Mao, Wang, Wu, Ding, Lu, Shen, Dai and Shen</copyright-holder><license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the <ext-link ext-link-type="uri" xlink:href="http://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution License (CC BY)</ext-link>. The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license>
</permissions>
<abstract><sec><title>Objective</title>
<p>This study compared the value of different systemic immune-inflammatory markers for evaluating coronary collateralization (CC) in patients with type 2 diabetes mellitus (T2DM) and chronic total occlusion (CTO).</p>
</sec><sec><title>Methods</title>
<p>Systemic immune-inflammation index (SII), systemic in&#xFB02;ammation response index (SIRI) and pan-immune-in&#xFB02;ammation value (PIV) were calculated at admission in 1409 T2DM patients with CTO. The degree of coronary collaterals was estimated using the Rentrop scoring system and categorized into poor (Rentrop score 0 or 1) or good (Rentrop score 2 or 3) CC. The predictors of poor CC were determined by multivariate regression analysis, and the diagnostic potential of these indexes was analyzed by Receiver Operating Characteristic (ROC) curves.</p>
</sec><sec><title>Results</title>
<p>SII, SIRI and PIV levels increased stepwise across Rentrop score 0&#x2013;3, with significantly higher levels in patients with poor CC than in those with good CC (<italic>P</italic>&#x2009;&#x003C;&#x2009;0.001). After adjusting for confounders, SII, SIRI and PIV (per tertile) remained independent factors for poor CC. SII predicted poor CC better than SIRI and PIV (AUC: 0.758 vs. 0.680 and 0.698, all <italic>P</italic>&#x2009;&#x003C;&#x2009;0.001). There existed an interaction between blood concentration of HbA1c and SII (<italic>P</italic>&#x2009;&#x003C;&#x2009;0.001), with high SII levels being associated with a greater risk (OR: 5.058 vs. 2.444) and providing a better predictive ability for poor CC (AUC: 0.817 vs. 0.731) in patients with HbA1c&#x2009;&#x003C;&#x2009;6.5&#x0025; compared to those with HbA1c&#x2009;&#x2265;&#x2009;6.5&#x0025;.</p>
</sec><sec><title>Conclusion</title>
<p>Our study shows that elevated SII provides a better prediction for poor CC in T2DM patients with CTO especially at good glycemic control.</p>
</sec>
</abstract>
<kwd-group>
<kwd>systemic immune-inflammation index</kwd>
<kwd>coronary collateral circulation</kwd>
<kwd>type 2 diabetes mellitus</kwd>
<kwd>stable coronary artery disease</kwd>
<kwd>chronic total occlusion</kwd>
</kwd-group><contract-num rid="cn001">82370409, 82170417, 81870357</contract-num><contract-sponsor id="cn001">National Natural Science Foundation of China</contract-sponsor><counts>
<fig-count count="5"/>
<table-count count="2"/><equation-count count="0"/><ref-count count="41"/><page-count count="13"/><word-count count="0"/></counts><custom-meta-wrap><custom-meta><meta-name>section-at-acceptance</meta-name><meta-value>Coronary Artery Disease</meta-value></custom-meta></custom-meta-wrap>
</article-meta>
</front>
<body><sec id="s1" sec-type="intro"><title>Introduction</title>
<p>Coronary collateralization (CC) is an adaptive response to transient or permanent coronary artery occlusion (<xref ref-type="bibr" rid="B1">1</xref>, <xref ref-type="bibr" rid="B2">2</xref>). The clinical relevance of the status of CC has been extensively investigated, showing that robust coronary collaterals are frequently associated with a favorable outcome by protecting ischemic myocardium, improving cardiac function, and decreasing future cardiovascular events and mortality (<xref ref-type="bibr" rid="B3">3</xref>, <xref ref-type="bibr" rid="B4">4</xref>). Collateral formation is a complex multi-step process involving an array of pro-angiogenic and anti-angiogenic factors (<xref ref-type="bibr" rid="B5">5</xref>). Type 2 diabetes mellitus (T2DM) is considered as a major risk factor for severe and diffuse coronary atherosclerosis and poor clinical outcome, and T2DM patients with chronic total occlusion (CTO) are more prone to develop poor CC compared to non-diabetic counterparts (<xref ref-type="bibr" rid="B6">6</xref>, <xref ref-type="bibr" rid="B7">7</xref>). Previous studies demonstrated that chronic low-grade inflammation, along with immune dysregulation, is a common mechanism of both atherosclerosis and T2DM, which may lead to impaired arteriogenesis and angiogenesis as well as new vessel growth in response to ischemia (<xref ref-type="bibr" rid="B8">8</xref>).</p>
<p>Systemic immune-inflammation index (SII), systemic inflammation response index (SIRI) and pan-immune-in&#xFB02;ammation-value (PIV) have been emerged as novel markers by integrating three subtypes of white blood cell and platelets and indicate the balance between the inflammatory response and immune status (<xref ref-type="bibr" rid="B9">9</xref>). Numerous studies have suggested that SII and SIRI are associated with atherogenesis and cardiovascular outcome (<xref ref-type="bibr" rid="B9">9</xref>&#x2013;<xref ref-type="bibr" rid="B11">11</xref>). Recently, Kelesoglu (<xref ref-type="bibr" rid="B10">10</xref>), Adali (<xref ref-type="bibr" rid="B12">12</xref>) and co-workers reported that high SII levels were correlated significantly with poor CC in patients with CTO. Yilmaz et.al demonstrated that PIV independently predicted poor CC in stable coronary artery disease patients (<xref ref-type="bibr" rid="B13">13</xref>). However, the value of systemic immune-inflammatory markers in the evaluation of angiographic CC in patients with T2DM and CTO remains unclear, mostly because of the small sample size and heterogenous population in the previous studies. Here, we investigated the relationship of SII, SIRI and PIV to coronary collateral formation in a large cohort of T2DM patients with CTO. The predictive value of elevated SII, SIRI and PIV for poor CC was also compared in relation to the status of glycemic control.</p>
</sec>
<sec id="s2" sec-type="methods"><title>Methods</title>
<p>This study was part of the COLLECT study (<bold>CO</bold>ronary Co<bold>LL</bold>ateralization in Type 2 diab<bold>E</bold>tic Patients with <bold>C</bold>hronic <bold>T</bold>otal Occlusion) registered with <ext-link ext-link-type="uri" xlink:href="https://www.ClinicalTrials.gov">ClinicalTrials.gov</ext-link> (NCT06054126), which aimed to explore the risk factors and treatment options for poor collateralization in T2DM patients with CTO. All participants provided written informed consent. The study protocol was approved by the Ethics Committee of Shanghai Ruijin Hospital, Shanghai Jiao and the study was conducted in accordance with the Declaration of Helsinki.</p>
<sec id="s2a"><title>Study population</title>
<p>A total of 1,503 consecutive stable angina patients who had T2DM between January 2010 and March 2024 were screened. All patients were &#x2265;18 years in age and had at least one lesion with angiographic 100&#x0025; occlusion in major epicardial coronary arteries for more than 3 months. This angiographic inclusion was used based on well-established knowledge that a severe coronary artery obstruction was a prerequisite for spontaneous collateral recruitment. For the purpose of the study, 94 patients were excluded because of severe chronic kidney disease requiring dialysis (<italic>n</italic>&#x2009;&#x003D;&#x2009;13), malignant tumor and pulmonary heart disease or immune system disorders (<italic>n</italic>&#x2009;&#x003D;&#x2009;10), history of coronary artery bypass grafting (<italic>n</italic>&#x2009;&#x003D;&#x2009;30), severe chronic heart failure (New York Heart Association functional class III or IV) (<italic>n</italic>&#x2009;&#x003D;&#x2009;6), or percutaneous coronary intervention (PCI) within the prior 3 months (<italic>n</italic>&#x2009;&#x003D;&#x2009;35). The remaining 1,409 T2DM patients with CTO were included in the final analysis (<xref ref-type="fig" rid="F1">Figure&#x00A0;1</xref>).</p>
<fig id="F1" position="float"><label>Figure 1</label>
<caption><p>Flowchart of the study. T2DM type 2, diabetes mellitus; CTO, chronic total occlusion; PCI, percutaneous coronary intervention; SII, systemic immune-inflammation index; SIRI, systemic inflammation response index; PIV, pan-immune-in&#xFB02;ammation value; CC, coronary collateralization.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fcvm-11-1490498-g001.tif"/>
</fig>
<p>Baseline clinical characteristics were collected from the Inpatient Medical Record Management Systems. Blood samples were obtained within 24&#x2005;h of hospital admission, and hematological and biochemical data were measured by standard laboratory techniques. Laboratory personnel unaware of the patient&#x0027;s diagnoses analyzed the blood samples. SII, SIRI and PIV were calculated based on the following formula: SII&#x2009;&#x003D;&#x2009;(neutrophil count&#x2009;&#x00D7;&#x2009;platelet count)/lymphocyte count; SIRI&#x2009;&#x003D;&#x2009;(neutrophil count&#x2009;&#x00D7;&#x2009;monocyte count)/lymphocyte count; PIV&#x2009;&#x003D;&#x2009;(monocyte count&#x2009;&#x00D7;&#x2009;neutrophil count&#x2009;&#x00D7;&#x2009;platelet count)/lymphocyte count (<xref ref-type="bibr" rid="B13">13</xref>, <xref ref-type="bibr" rid="B14">14</xref>).</p>
<p>The diagnosis for T2DM was made according to the American Diabetes Association guidelines (<xref ref-type="bibr" rid="B14">14</xref>). Hypertension was diagnosed as the presence of office systolic blood pressure values &#x2265;140&#x2005;mmHg and/or diastolic blood pressure values &#x2265;90&#x2005;mmHg, or taking antihypertensive drugs for blood pressure control (<xref ref-type="bibr" rid="B15">15</xref>). Hypercholesterolemia was defined according to the Third Report of The National Cholesterol Education Program (NCEP) (<xref ref-type="bibr" rid="B16">16</xref>). Severe chronic kidney disease was defined as estimated glomerular filtration rate (eGFR)&#x2009;&#x003C;&#x2009;15&#x2005;ml/(min&#x00B7;1.73&#x2005;m<sup>2</sup>) (<xref ref-type="bibr" rid="B17">17</xref>).</p>
</sec>
<sec id="s2b"><title>Coronary angiography and collateral grading</title>
<p>Coronary angiography was performed via the femoral or radial approach, and the degree of coronary artery narrowing was determined by quantitative coronary analysis (QCA) (<xref ref-type="bibr" rid="B18">18</xref>). Number of significant diseased coronary arteries (&#x2265;50&#x0025; stenosis in major epicardial coronary artery) was used to assess coronary disease severity, and left main coronary stenosis was considered as 2-vessel disease (<xref ref-type="bibr" rid="B19">19</xref>).</p>
<p>Presence/absence and extent of collateral circulation were graded according to the Rentrop scoring system (<xref ref-type="bibr" rid="B20">20</xref>). Rentrop score 0 (no filling of any collateral vessels) and score 1 (filling of side branches of the artery by collateral vessels without visualization of the epicardial segment) were categorized into poor CC, whereas Rentrop score 2 (partial filling of the epicardial segment by collateral vessels) and score 3 (complete filling of the epicardial artery by collateral vessels) were classified into good CC. For patients with more than one chronic total occlusion, the vessel with the highest collateral grade was selected for analysis. Coronary collaterals were graded by two experienced interventional cardiologists blinded to patient&#x0027;s clinical characteristics. Any disagreement was resolved by a third reviewer.</p>
</sec>
<sec id="s2c"><title>Statistical analysis</title>
<p>Continuous variables are presented as mean&#x2009;&#x00B1;&#x2009;standard deviations (SD) or median (interquartile range, IQR), and were compared between groups by Student&#x0027;s <italic>t</italic>-test and Mann&#x2013;Whitney <italic>U</italic> test for normally or non-normally distributed variables, respectively. Categorical variables are expressed as absolute number with percentage and were compared between groups by Chi-square test. One-way ANOVA analysis was performed to compare the difference of SII, SIRI and PIV between groups with 0&#x2013;3 Rentrop score. To determine the independent predictors for poor CC, age, female gender, body mass index (BMI), hypertension, hypercholesterolemia, hematological data, eGFR and HbA1c together with SII, SIRI or PIV were adopted in multivariate logistic regression model 1&#x2013;3, respectively. Receiver Operating Characteristic (ROC) analysis was made, and the predictive ability of SII, SIRI and PIV for poor CC in T2DM patients with CTO was evaluated by the area under the ROC curve (AUC). The Youden index was applied to find the optimal cutoff point for maximized sensitivity and specificity. The comparisons of AUCs were performed using DeLong test. All statistical analyses were done using SPSS version 26.0 (SPSS Inc., Chicago, IL, USA) and MedCalc software (Version 20.0.22; Medcalc Software, Mariakerke, Belgium). Statistical significance was set a two-tailed <italic>P</italic> value&#x2009;&#x003C;&#x2009;0.05.</p>
</sec>
</sec>
<sec id="s3" sec-type="results"><title>Results</title>
<sec id="s3a"><title>Baseline characteristics</title>
<p>Poor and good CC were detected in 618 (43.9&#x0025;) and 791 (56.1&#x0025;) patients, respectively. Compared to patients with good CC, those with poor CC were older and more female in gender, and had higher incidence of hypertension, hypercholesterolemia and prior myocardial infarction. As for laboratory measurements, platelet count, white blood cell count and neutrophil were higher, and fasting blood glucose (FBG), glycosylated hemoglobin (HbA1c), total cholesterol, low-density lipoprotein cholesterol (LDL-C) and blood urea nitrogen (BUN) were elevated, but monocyte, lymphocyte and eGFR were lower in patients with poor CC (<italic>P</italic>&#x2009;&#x003C;&#x2009;0.05 for all comparisons). The two groups did not significantly differ with respective to severity of coronary artery disease and medications (<xref ref-type="table" rid="T1">Table&#x00A0;1</xref>).</p>
<table-wrap id="T1" position="float"><label>Table 1</label>
<caption><p>Baseline characteristics of the study patients.</p></caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th valign="top" align="left">Variables</th>
<th valign="top" align="center">Poor CC (<italic>n</italic>&#x2009;&#x003D;&#x2009;618)</th>
<th valign="top" align="center">Good CC (<italic>n</italic>&#x2009;&#x003D;&#x2009;791)</th>
<th valign="top" align="center"><italic>P</italic> value</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">Age, years</td>
<td valign="top" align="center">66.1&#x2009;&#x00B1;&#x2009;10.5</td>
<td valign="top" align="center">63.0&#x2009;&#x00B1;&#x2009;11.0</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Female, No. (&#x0025;)</td>
<td valign="top" align="center">159 (25.7)</td>
<td valign="top" align="center">139 (17.6)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Body mass index, kg/m<sup>2</sup></td>
<td valign="top" align="center">25.27&#x2009;&#x00B1;&#x2009;3.01</td>
<td valign="top" align="center">25.03&#x2009;&#x00B1;&#x2009;3.00</td>
<td valign="top" align="center">0.145</td>
</tr>
<tr>
<td valign="top" align="left">SBP (mmHg)</td>
<td valign="top" align="center">136.9&#x2009;&#x00B1;&#x2009;21.9</td>
<td valign="top" align="center">135.8&#x2009;&#x00B1;&#x2009;19.7</td>
<td valign="top" align="center">0.307</td>
</tr>
<tr>
<td valign="top" align="left">DBP (mmHg)</td>
<td valign="top" align="center">76.7&#x2009;&#x00B1;&#x2009;12.3</td>
<td valign="top" align="center">77.2&#x2009;&#x00B1;&#x2009;12.1</td>
<td valign="top" align="center">0.448</td>
</tr>
<tr>
<td valign="top" align="left">Smoking, No. (&#x0025;)</td>
<td valign="top" align="center">240 (38.8)</td>
<td valign="top" align="center">298 (37.7)</td>
<td valign="top" align="center">0.659</td>
</tr>
<tr>
<td valign="top" align="left">Hypertension, No. (&#x0025;)</td>
<td valign="top" align="center">472 (76.4)</td>
<td valign="top" align="center">555 (70.2)</td>
<td valign="top" align="center">0.009</td>
</tr>
<tr>
<td valign="top" align="left">Hypercholesterolemia, No. (&#x0025;)</td>
<td valign="top" align="center">174 (28.2)</td>
<td valign="top" align="center">150 (19.0)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Prior MI, No. (&#x0025;)</td>
<td valign="top" align="center">128 (20.7)</td>
<td valign="top" align="center">130 (16.4)</td>
<td valign="top" align="center">0.044</td>
</tr>
<tr>
<td valign="top" align="left">Platelet, 10<sup>9</sup>/L</td>
<td valign="top" align="center">200.0 (167.0&#x2013;242.0)</td>
<td valign="top" align="center">187.0 (154.0&#x2013;221.0)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">White blood cell count, 10<sup>9</sup>/L</td>
<td valign="top" align="center">7.63 (6.37&#x2013;9.50)</td>
<td valign="top" align="center">6.80 (5.73&#x2013;8.10)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Neutrophil, 10<sup>9</sup>/L</td>
<td valign="top" align="center">5.35 (4.27&#x2013;7.00)</td>
<td valign="top" align="center">4.20 (3.47&#x2013;5.28)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Lymphocyte, 10<sup>9</sup>/L</td>
<td valign="top" align="center">1.41 (1.07&#x2013;1.89)</td>
<td valign="top" align="center">1.69 (1.33&#x2013;2.07)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Monocyte, 10<sup>9</sup>/L</td>
<td valign="top" align="center">0.50 (0.40&#x2013;0.61)</td>
<td valign="top" align="center">0.51 (0.40&#x2013;0.68)</td>
<td valign="top" align="center">0.016</td>
</tr>
<tr>
<td valign="top" align="left">SII</td>
<td valign="top" align="center">808.43 (490.99&#x2013;1,221.09)</td>
<td valign="top" align="center">466.64 (327.56&#x2013;655.71)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">SIRI</td>
<td valign="top" align="center">2.15 (1.32&#x2013;2.97)</td>
<td valign="top" align="center">1.30 (0.87&#x2013;2.08)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">PIV</td>
<td valign="top" align="center">443.21 (263.55&#x2013;634.68)</td>
<td valign="top" align="center">236.17 (149.58&#x2013;407.62)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Fasting glucose, mmol/L</td>
<td valign="top" align="center">7.02 (5.65&#x2013;8.63)</td>
<td valign="top" align="center">6.60 (5.35&#x2013;7.79)</td>
<td valign="top" align="center">0.002</td>
</tr>
<tr>
<td valign="top" align="left">HbA1c,&#x0025;</td>
<td valign="top" align="center">7.10 (6.30&#x2013;8.20)</td>
<td valign="top" align="center">7.00 (6.20&#x2013;8.00)</td>
<td valign="top" align="center">0.001</td>
</tr>
<tr>
<td valign="top" align="left">Triglyceride, mmol/L</td>
<td valign="top" align="center">1.53 (1.08&#x2013;2.11)</td>
<td valign="top" align="center">1.44 (1.07&#x2013;1.99)</td>
<td valign="top" align="center">0.160</td>
</tr>
<tr>
<td valign="top" align="left">Total cholesterol, mmol/L</td>
<td valign="top" align="center">3.96 (3.22&#x2013;4.81)</td>
<td valign="top" align="center">3.81 (3.14&#x2013;4.62)</td>
<td valign="top" align="center">0.011</td>
</tr>
<tr>
<td valign="top" align="left">LDL-C, mmol/L</td>
<td valign="top" align="center">2.13 (1.46&#x2013;2.95)</td>
<td valign="top" align="center">1.98 (1.35&#x2013;2.75)</td>
<td valign="top" align="center">0.012</td>
</tr>
<tr>
<td valign="top" align="left">HDL-C, mmol/L</td>
<td valign="top" align="center">0.98 (0.85&#x2013;1.13)</td>
<td valign="top" align="center">0.96 (0.83&#x2013;1.12)</td>
<td valign="top" align="center">0.086</td>
</tr>
<tr>
<td valign="top" align="left">BUN, mmol/L</td>
<td valign="top" align="center">6.10 (4.90&#x2013;7.80)</td>
<td valign="top" align="center">5.80 (4.80&#x2013;7.00)</td>
<td valign="top" align="center">0.005</td>
</tr>
<tr>
<td valign="top" align="left">Creatinine, &#x03BC;mol/L</td>
<td valign="top" align="center">82.0 (69.0&#x2013;98.0)</td>
<td valign="top" align="center">80.0 (68.0&#x2013;93.0)</td>
<td valign="top" align="center">0.055</td>
</tr>
<tr>
<td valign="top" align="left">Uric acid, &#x03BC;mol/L</td>
<td valign="top" align="center">329.0 (273.0&#x2013;395.0)</td>
<td valign="top" align="center">331.0 (278.0&#x2013;398.0)</td>
<td valign="top" align="center">0.762</td>
</tr>
<tr>
<td valign="top" align="left">hsCRP, mg/L</td>
<td valign="top" align="center">2.90 (1.00&#x2013;8.20)</td>
<td valign="top" align="center">2.56 (0.91&#x2013;6.91)</td>
<td valign="top" align="center">0.058</td>
</tr>
<tr>
<td valign="top" align="left">eGFR, ml/min/1.73&#x2005;m<sup>2</sup></td>
<td valign="top" align="center">81.91 (65.21&#x2013;95.13)</td>
<td valign="top" align="center">86.48 (71.83&#x2013;96.93)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left" colspan="4">Severity of CAD</td>
</tr>
<tr>
<td valign="top" align="left">One-vessel disease</td>
<td valign="top" align="center">87 (14.1)</td>
<td valign="top" align="center">94 (11.9)</td>
<td valign="top" align="center">0.230</td>
</tr>
<tr>
<td valign="top" align="left">Two-vessel disease</td>
<td valign="top" align="center">168 (27.2)</td>
<td valign="top" align="center">210 (26.5)</td>
<td valign="top" align="center">0.809</td>
</tr>
<tr>
<td valign="top" align="left">Three-vessel disease</td>
<td valign="top" align="center">363 (58.7)</td>
<td valign="top" align="center">487 (61.6)</td>
<td valign="top" align="center">0.297</td>
</tr>
<tr>
<td valign="top" align="left" colspan="4">Medication</td>
</tr>
<tr>
<td valign="top" align="left">ACE inhibitor/ARBs</td>
<td valign="top" align="center">349 (56.5)</td>
<td valign="top" align="center">438 (55.4)</td>
<td valign="top" align="center">0.705</td>
</tr>
<tr>
<td valign="top" align="left">&#x03B2;-blockers</td>
<td valign="top" align="center">443 (71.7)</td>
<td valign="top" align="center">554 (70.0)</td>
<td valign="top" align="center">0.517</td>
</tr>
<tr>
<td valign="top" align="left">Calcium channel blockers</td>
<td valign="top" align="center">190 (30.7)</td>
<td valign="top" align="center">216 (27.3)</td>
<td valign="top" align="center">0.173</td>
</tr>
<tr>
<td valign="top" align="left">Nitrates</td>
<td valign="top" align="center">243 (39.3)</td>
<td valign="top" align="center">336 (42.5)</td>
<td valign="top" align="center">0.230</td>
</tr>
<tr>
<td valign="top" align="left">Diuretic</td>
<td valign="top" align="center">127(20.6)</td>
<td valign="top" align="center">146(18.5)</td>
<td valign="top" align="center">0.342</td>
</tr>
<tr>
<td valign="top" align="left">Statins</td>
<td valign="top" align="center">556(90.0)</td>
<td valign="top" align="center">704(89.0)</td>
<td valign="top" align="center">0.601</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="table-fn1"><p>CC, coronary collateralization; SBP, Systolic blood pressure; DBP, diastolic blood pressure; MI, myocardial infarction; SII, systemic immune-inflammation index; SIRI, systemic inflammation response index; PIV, pan-immune-in&#xFB02;ammation value; HbA1c, glycosylated hemoglobin A1c; LDL-C, low-density lipoprotein cholesterol; HDL-C, high-density lipoprotein cholesterol; Lp(a), lipoprotein a; BUN, blood urea nitrogen; hsCRP, high-sensitivity C-reactive protein; eGFR, estimated glomerular filtration rate.</p></fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="s3b"><title>SII, SIRI and PIV with coronary collateralization</title>
<p>SII, SIRI and PIV levels increased stepwise across Rentrop score 0&#x2013;3 (<xref ref-type="fig" rid="F2">Figure&#x00A0;2</xref>), with significantly higher levels in patients with poor CC compared to those with good CC [SII: 808.43(490.99&#x2013;1,221.09) vs. 466.64 (327.56&#x2013;655.71); SIRI: 2.15(1.32&#x2013;2.97) vs. 1.30 (0.87&#x2013;2.08); PIV: 443.21(263.55&#x2013;634.68) vs. 236.17(149.58&#x2013;407.62), all <italic>P</italic>&#x2009;&#x003C;&#x2009;0.001] (<xref ref-type="table" rid="T1">Table&#x00A0;1</xref>). Increased SII tertiles (OR, 3.005; 95&#x0025; CI, 2.589&#x2013;3.489; <italic>P</italic>&#x2009;&#x003C;&#x2009;0.001), SIRI tertiles (OR, 2.111; 95&#x0025; CI, 1.839&#x2013;2.424; <italic>P</italic>&#x2009;&#x003C;&#x2009;0.001) and PIV tertiles (OR, 2.244; 95&#x0025; CI, 1.951&#x2013;2.581; <italic>P</italic>&#x2009;&#x003C;&#x2009;0.001) were associated with a higher proportion of poor CC, respectively (<xref ref-type="fig" rid="F2">Figure&#x00A0;2</xref>).</p>
<fig id="F2" position="float"><label>Figure 2</label>
<caption><p>Relationship of SII, SIRI and PIV with rentrop score in T2DM patients with CTO. SII, SIRI and PIV decreased gradually across Rentrop score 0&#x2013;3 [<bold>(A)&#x2013;(C)</bold>, &#x002A;&#x002A;&#x002A;&#x002A;<italic>P</italic>&#x2009;&#x003C;&#x2009;0.0001]. The proportion of poor CC increased from the lowest tertile to the highest tertile of SII, SIRI and PIV <bold>(D)&#x2013;(F)</bold>.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fcvm-11-1490498-g002.tif"/>
</fig>
<p>Multivariate logistic regression analysis revealed that after adjustment for confounding factors including age, gender, BMI, hypercholesterolemia, hematological data, HbA1c and eGFR, high tertile of SII, SIRI and PIV levels remained independent predictors for poor CC in T2DM patients with CTO (<xref ref-type="table" rid="T2">Table&#x00A0;2</xref>).</p>
<table-wrap id="T2" position="float"><label>Table 2</label>
<caption><p>Multivariate analysis of risk factors for poor CC in T2DM patients with CTO.</p></caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="left"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th valign="top" align="left"/>
<th valign="top" align="center">Variable</th>
<th valign="top" align="center">OR (95&#x0025; CI)</th>
<th valign="top" align="center"><italic>P</italic> value</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left" rowspan="8">Model 1</td>
<td valign="top" align="left">Age (per 10 years)</td>
<td valign="top" align="center">1.319 (1.165&#x2013;1.493)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Female</td>
<td valign="top" align="center">1.333 (0.992&#x2013;1.790)</td>
<td valign="top" align="center">0.057</td>
</tr>
<tr>
<td valign="top" align="left">Body mass index (per SD)</td>
<td valign="top" align="center">1.184 (1.049&#x2013;1.336)</td>
<td valign="top" align="center">0.006</td>
</tr>
<tr>
<td valign="top" align="left">Hypertension</td>
<td valign="top" align="center">1.205 (0.919&#x2013;1.579)</td>
<td valign="top" align="center">0.177</td>
</tr>
<tr>
<td valign="top" align="left">Hypercholesterolemia</td>
<td valign="top" align="center">1.555 (1.175&#x2013;2.057)</td>
<td valign="top" align="center">0.002</td>
</tr>
<tr>
<td valign="top" align="left">HbA1c (per SD)</td>
<td valign="top" align="center">1.179 (1.046&#x2013;1.328)</td>
<td valign="top" align="center">0.007</td>
</tr>
<tr>
<td valign="top" align="left">eGFR (per SD)</td>
<td valign="top" align="center">0.954 (0.841&#x2013;1.083)</td>
<td valign="top" align="center">0.469</td>
</tr>
<tr>
<td valign="top" align="left">SII (per tertile)</td>
<td valign="top" align="center">2.959 (2.537&#x2013;3.451)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left" rowspan="8">Model 2</td>
<td valign="top" align="left">Age (per 10 years)</td>
<td valign="top" align="center">1.261 (1.121&#x2013;1.419)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Female</td>
<td valign="top" align="center">1.630 (1.224&#x2013;2.170)</td>
<td valign="top" align="center">0.001</td>
</tr>
<tr>
<td valign="top" align="left">Body mass index (per SD)</td>
<td valign="top" align="center">1.152 (1.025&#x2013;1.295)</td>
<td valign="top" align="center">0.017</td>
</tr>
<tr>
<td valign="top" align="left">Hypertension</td>
<td valign="top" align="center">1.211 (0.934&#x2013;1.571)</td>
<td valign="top" align="center">0.149</td>
</tr>
<tr>
<td valign="top" align="left">Hypercholesterolemia</td>
<td valign="top" align="center">1.663 (1.271&#x2013;2.177)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">HbA1c (per SD)</td>
<td valign="top" align="center">1.238 (1.104&#x2013;1.389)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">eGFR (per SD)</td>
<td valign="top" align="center">0.945 (0.836&#x2013;1.069)</td>
<td valign="top" align="center">0.372</td>
</tr>
<tr>
<td valign="top" align="left">SIRI (per tertile)</td>
<td valign="top" align="center">2.146 (1.857&#x2013;2.480)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left" rowspan="8">Model 3</td>
<td valign="top" align="left">Age (per 10 years)</td>
<td valign="top" align="center">1.304 (1.158&#x2013;1.469)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
<tr>
<td valign="top" align="left">Female</td>
<td valign="top" align="center">1.466 (1.103&#x2013;1.951)</td>
<td valign="top" align="center">0.009</td>
</tr>
<tr>
<td valign="top" align="left">Body mass index (per SD)</td>
<td valign="top" align="center">1.149 (1.021&#x2013;1.293)</td>
<td valign="top" align="center">0.021</td>
</tr>
<tr>
<td valign="top" align="left">Hypertension</td>
<td valign="top" align="center">1.198 (0.922&#x2013;1.555)</td>
<td valign="top" align="center">0.176</td>
</tr>
<tr>
<td valign="top" align="left">Hypercholesterolemia</td>
<td valign="top" align="center">1.588 (1.212&#x2013;2.081)</td>
<td valign="top" align="center">0.001</td>
</tr>
<tr>
<td valign="top" align="left">HbA1c (per SD)</td>
<td valign="top" align="center">1.197 (1.066&#x2013;1.343)</td>
<td valign="top" align="center">0.002</td>
</tr>
<tr>
<td valign="top" align="left">eGFR (per SD)</td>
<td valign="top" align="center">0.928 (0.820&#x2013;1.049)</td>
<td valign="top" align="center">0.231</td>
</tr>
<tr>
<td valign="top" align="left">PIV (per tertile)</td>
<td valign="top" align="center">2.230 (1.929&#x2013;2.578)</td>
<td valign="top" align="center">&#x003C;0.001</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="table-fn2"><p>Abbreviations are as in <xref ref-type="table" rid="T1">Table&#x00A0;1</xref>.</p></fn>
</table-wrap-foot>
</table-wrap>
<p>In ROC analysis, the likelihood that a cutoff value of SII 703.86 could accurately differentiate patients with poor CC from those with good CC was 75.8&#x0025; (95&#x0025; CI, 0.735&#x2013;0.781), with 61.2&#x0025; sensitivity and 80.1&#x0025; specificity. SII had a significantly better predictive ability for poor CC than SIRI (AUC: 0.680, 95&#x0025; CI, 0.655&#x2013;0.704) and PIV (AUC: 0.698, 95&#x0025; CI, 0.673&#x2013;0.722) (all <italic>P</italic>&#x2009;&#x003C;&#x2009;0.001) (<xref ref-type="fig" rid="F3">Figure&#x00A0;3</xref>).</p>
<fig id="F3" position="float"><label>Figure 3</label>
<caption><p>Value of SII <bold>(A)</bold> and <bold>(B)</bold>, SIRI <bold>(C)</bold> and PIV <bold>(D)</bold> for predicting poor coronary collateralization. According to the ROC analysis, SII showed better predictive ability of poor CC compared to SIRI and PIV. The likelihood that a cutoff value of SII 703.86 could accurately differentiate patients with poor CC from those with good CC was 75.8&#x0025;, with 61.2&#x0025; sensitivity and 80.1&#x0025; specificity <bold>(A)</bold> and <bold>(B)</bold>. The likelihood that a cutoff value of SIRI 1.93 could accurately differentiate patients with poor CC from those with good CC was 68.0&#x0025;, with 59.5&#x0025; sensitivity and 72.1&#x0025; specificity <bold>(C)</bold>. The likelihood that a cutoff value of PIV 299.64 could accurately differentiate patients with poor CC from those with good CC was 69.8&#x0025;, with 71.2&#x0025; sensitivity and 64.6&#x0025; specificity <bold>(D)</bold>.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fcvm-11-1490498-g003.tif"/>
</fig>
</sec>
<sec id="s3c"><title>Influence of glycemic control</title>
<p>After stratifying the study population by age, gender, BMI, hypercholesterolemia, eGFR and HbA1c, increased SII, SIRI and PIV levels showed consistent predictive value for poor CC with odds ratio (OR) ranging from 1.937 to 5.058. No interactions of SII, SIRI and PIV with age, gender, BMI, hypertension, hypercholesterolemia, and eGFR on poor CC were observed (<italic>P</italic> for interaction &#x003E;0.05). However, there existed a significant interaction between blood concentration of HbA1c and SII on poor CC (<italic>P</italic> for interaction &#x003C;0.001). Compared to patients with HbA1c&#x2009;&#x2265;&#x2009;6.5&#x0025;, high SII values were associated with a greater risk (OR: 5.058 vs. 2.444) (<xref ref-type="fig" rid="F4">Figure&#x00A0;4</xref>) and provided a better predictive ability (AUC: 0.817 vs. 0.731) for poor CC in those with HbA1c&#x2009;&#x003C; 6.5&#x0025; (<xref ref-type="fig" rid="F5">Figure&#x00A0;5</xref>).</p>
<fig id="F4" position="float"><label>Figure 4</label>
<caption><p>Diagnostic value of SII (top), SIRI (middle), and PIV (bottom) in subgroup analysis.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fcvm-11-1490498-g004.tif"/>
</fig>
<fig id="F5" position="float"><label>Figure 5</label>
<caption><p>Value of SII for predicting poor CC in patients with good <bold>(A)</bold> or poor glycemic control <bold>(B)</bold>.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fcvm-11-1490498-g005.tif"/>
</fig>
</sec>
</sec>
<sec id="s4" sec-type="discussion"><title>Discussion</title>
<p>Our results showed that (1) systemic immune-inflammatory markers including SII, SIRI, and PIV were associated with angiographic CC in T2DM patients with CTO; (2) SII provided a significantly better predictive ability for poor CC than SIRI and PIV; (3) high SII levels conferred a greater risk and had a better prediction for poor CC in patients with HbA1c&#x2009;&#x003C;&#x2009;6.5&#x0025; as compared to those with HbA1c&#x2009;&#x2265;&#x2009;6.5&#x0025;.</p>
<p>It is well recognized that collateral formation is impaired in T2DM patients and CTO, however, the underlying mechanism remains not fully understood. Previous studies have shown that chronic low-grade inflammation plays a central role in the pathophysiology of coronary collateral development (<xref ref-type="bibr" rid="B21">21</xref>). Patients with T2DM have a persistent inflammatory status, which could decrease production of nitric oxide and increase production of reactive oxygen species, leading to elevated oxidative stress and endothelial dysfunction (<xref ref-type="bibr" rid="B22">22</xref>&#x2013;<xref ref-type="bibr" rid="B24">24</xref>). This supports the view that inflammation-related markers might provide predictive value on CC in T2DM patients with CTO. Several readily available inflammatory biomarkers including high-sensitivity C-reactive protein (hsCRP), neutrophil, monocyte, platelet (PLT), neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR) have been found to be associated with CC in patients with CTO (<xref ref-type="bibr" rid="B25">25</xref>&#x2013;<xref ref-type="bibr" rid="B28">28</xref>). However, the inflammatory markers that are composed of a single component (neutrophil, lymphocyte, or platelet) and two components (NLR and PLR) are often affected by other confounding factors and become relatively weak predictors of prognosis. SII, SIRI and PIV are integrated markers of systemic immune-inflammation and their role in the evaluation of cardiovascular diseases has been recently studied (<xref ref-type="bibr" rid="B29">29</xref>&#x2013;<xref ref-type="bibr" rid="B31">31</xref>). SII obtained by multiplying NLR and platelet increases in the presence of chronic inflammation, and it is a relatively strong inflammatory marker that may inhibit endothelial progenitor cell differentiation, survival, and function&#x2014;key components of angiogenesis. SII was thought to be more reliable and representative of in&#xFB02;ammation and thrombosis than PLR and NLR (<xref ref-type="bibr" rid="B32">32</xref>, <xref ref-type="bibr" rid="B33">33</xref>). Dziedzic et al. demonstrated a relationship of SII values with the severity of coronary artery disease (<xref ref-type="bibr" rid="B34">34</xref>). Xia et al. reported that high SII was significantly associated with increased all-cause and cardiovascular mortality risks (<xref ref-type="bibr" rid="B9">9</xref>). In the present study, we found that SII levels correlated closely with Rentrop score in T2DM patients with CTO. The predictive ability of SII on poor CC performed well even after adjusting for confounding factors and was much better than other inflammation indexes (SIRI and PIV). Mechanistically, elevated SII levels indicated the increased neutrophil and platelet counts and decreased lymphocyte counts. Neutrophils release inflammatory cytokines and reactive oxygen species, which may exacerbate endothelial dysfunction and inhibit angiogenesis (<xref ref-type="bibr" rid="B35">35</xref>). Low levels of lymphocytes reflect immune suppression and are associated with impaired endothelial function (<xref ref-type="bibr" rid="B36">36</xref>). Platelets play a vital role in new blood vessel formation by involving many angiogenesis promoters and inhibitors (<xref ref-type="bibr" rid="B37">37</xref>). Thus, elevated SII levels are associated with systemic inflammation, immune dysregulation, and impaired angiogenic processes. However, SIRI focuses more on monocytes and does not account for platelets, which is essential in angiogenesis and vascular remodeling. Although PIV includes platelet counts, the weights of the component are linearly distributed, which may obscure the dominant role of platelets. Taken together, it may explain why SII predicts poor CC more effectively than SIRI and PIV in T2DM patients with CTO.</p>
<p>In addition, the diagnostic performance of SII remained satisfied in different subgroup analysis. Interestingly, using HbA1c 6.5&#x0025; as the threshold of glycemic control, a significant interaction was identified when we analyzed the predictive value of SII on poor CC. High SII was associated with a greater risk and provided a significantly better prediction for poor CC in patients with HbA1c&#x2009;&#x003C;&#x2009;6.5&#x0025;, as compared to those with HbA1c&#x2009;&#x003E;&#x2009;6.5&#x0025;. The reason for that remains unclear, but our findings are, at least partly, supportive of previous reports which emphasize the relationship between inflammation and the development of coronary collaterals (<xref ref-type="bibr" rid="B10">10</xref>, <xref ref-type="bibr" rid="B12">12</xref>). We speculate that in T2DM patients with CTO and normal glycemic control, the systemic inflammatory condition is in relatively low grade. An increase in SII value could be more reliable indicator of a great risk for developing poor CC. In contrast, patients with poor glycemic control often have a high grade of inflammatory status as suggested by high baseline SII levels even in those with good CC, thus the effect of changes of SII were less remarkable for forecasting the risk of poor CC.</p>
<sec id="s4a"><title>Study limitations</title>
<p>The present study had several limitations. First, this was a single center retrospective and observational study, thus the selected population may not represent the whole aimed cohort, and the causal link of SII, SIRI and PIV with poor CC was not detected. Second, although several traditional risk factors were considered, there were still some confounding factors that were not included in the analysis. Third, the degree of coronary collateral circulation was estimated according to the Rentrop scoring system, whereas measurement of collateral flow index may be more accurate.</p>
</sec>
</sec>
<sec id="s5" sec-type="conclusions"><title>Conclusion and perspective</title>
<p>This study demonstrates that SII, SIRI, and PIV are closely associated with angiographic CC, and SII provides a better prediction for poor CC than SIRI and PIV in T2DM patients with CTO, especially at good glycemic control. The good predictive ability of SII on poor CC validated its potential as a diagnostic biomarker in T2DM patients with CTO. Since there is increasing evidence that treatment decisions and indications for recanalization of a CTO should be based not only on clinical characteristics and occluded lesion morphology, but also on collateral quality and myocardial viability (<xref ref-type="bibr" rid="B38">38</xref>&#x2013;<xref ref-type="bibr" rid="B41">41</xref>). SII shows CC status as a useful, simple, easily measurable, and cheap indicator, and could be used as a reference for clinicians to improve the care of diabetic patients with stable coronary artery disease. Further prospective studies with large sample size and long-term clinical follow-up are warranted to prove the diagnostic and prognostic value of SII, in relation to CC, for patients with T2DM and CTO.</p>
</sec>
</body>
<back>
<sec id="s6" sec-type="data-availability"><title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.</p>
</sec>
<sec id="s7" sec-type="ethics-statement"><title>Ethics statement</title>
<p>The studies involving humans were approved by Institutional Review Board of Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation was not required from the participants or the participants&#x2019; legal guardians/next of kin in accordance with the national legislation and institutional requirements.</p>
</sec>
<sec id="s8" sec-type="author-contributions"><title>Author contributions</title>
<p>LM: Formal Analysis, Software, Writing &#x2013; original draft. YW: Writing &#x2013; original draft, Formal Analysis, Software. ZW: Writing &#x2013; original draft, Data curation, Investigation, Methodology. FD: Data curation, Investigation, Writing &#x2013; original draft, Supervision. LL: Supervision, Writing &#x2013; original draft, Methodology, Project administration. WS: Project administration, Writing &#x2013; original draft, Conceptualization, Validation. YD: Writing &#x2013; original draft, Funding acquisition, Software. YS: Funding acquisition, Writing &#x2013; review &#x0026; editing.</p>
</sec>
<sec id="s9" sec-type="funding-information"><title>Funding</title>
<p>The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study received support from grants provided by the National Natural Science Foundation of China (82370409, 82170417, 81870357).</p>
</sec>
<sec id="s10" sec-type="COI-statement"><title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="s11" sec-type="disclaimer"><title>Publisher&#x0027;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
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